One evening last week, as the Senate debated the merits of the Liberal government's assisted-dying legislation, a new senator stood with a profound question.

"When there is an impasse between the Senate and the House of Commons, and the Senate expresses its will clearly and the House of Commons maintains its position, does there not come a time when the Senate has to give in to the popular majority expressed by the House of Commons?" asked André Pratte, less than two months into his time as a member of the Red Chamber.

This is the question that now hangs over Bill C-14, passed last night by the Senate with seven amendments, including a rewriting of the bill's provisions for who is eligible to receive medical assistance in dying.

It is now for the House to decide whether to accept or reject those changes.

If rejected, it will be for the Senate to decide how strenuously it is willing to insist on its desired version of the bill.

Most simply and more generally, the question for the Senate is this: When should the appointed Red Chamber defer to the democratically elected House of Commons? 

If one takes a dim view of the Senate's legitimacy, the answer to that question might be "always." If one is willing to accept that the Senate might exist for some practical purpose, the answer might at least be "not always right away."

It is not a new question, but it might be newly asked now if the Senate is embarking on an unprecedented era of independence and reduced partisanship.

When should the Senate intervene?

Testifying before the Senate's committee on modernization in April, Paul Thomas, the political studies scholar from the University of Manitoba, proposed that the upper chamber transform itself from "a house of political parties into a house of review," one that would enjoy greater freedom, but would still maintain a certain degree of legislative humility.

"The undoubted right of the Senate to defeat, delay or fundamentally modify bills … should be used sparingly, in exceptional cases when bills are considered dangerous, when they are fundamentally unsound and/or they are not easily reversed once put into action," he said.

The Salisbury convention, a British invention that suggests an appointed upper chamber should not overrule the elected House on bills related to the governing party's campaign promises, would take a great number of bills out of play.

But that would still leave bills like C-14, or C-7, the government's legislation on RCMP unionization, which a Senate committee amended on Tuesday. Looking forward, it might also give the Senate some basis to intervene on legislation to implement electoral reform. (The most philosophically fraught scenario: a chamber of political appointees insisting on a referendum before passing anything into law.)

The Senate must be "restrained and reasonable," Thomas adds via email, but he concedes that "reasonableness is to some extent in the eye of the beholder."

"If the House of Commons passes the identical bill twice, the Senate, almost without exception, should not seek to veto or further amend the bill," Thomas argues. "Only under extraordinary circumstances involving unconstitutional or highly dangerous bills should the Senate carry on a fight with the popularly elected House of Commons."

Of course, it is the constitutionality of the assisted-dying bill that is perhaps most at issue: the government insists the bill complies with the Charter of Rights and Freedoms, while various senators believe it does not meet the standard of the Supreme Court's decision in Carter vs. Canada.

But that raises the prospect of the two chambers deadlocked over competing guesses about what the Supreme Court might say.

MPs debate: Senate changes to C-1411:57

A complementary chamber, not a rival

"I think this is an important exercise for the Senate to exercise its role of review, thoughtful consideration and sending back advice," Frances Lankin, one of the newest senators, told CBC Radio's The House this past weekend. "That advice, in the end, could be rejected by the democratically elected Parliament."

"Advice" suggests a non-binding recommendation. Other senators might be less deferential.

"I do not think that this is a case where we simply make the amendments and the House just gives us the back of their hand, and we say, 'Well, we gave you our advice, you didn't take it, you're elected, we're appointed, we'll hold our nose and vote for it,'" says Liberal Senate leader James Cowan. "I'm not there. Yet."

Cowan says he views the Senate as a "complementary" chamber to the House, not a "rival." And, in theory, the Senate's appointed nature would impose a certain deference (one of the most significant knocks on an elected Senate is that it would increase the probability of legislative gridlock). 

But Cowan also says he won't support a bill he doesn't think is constitutional. And, historically, the Senate's deference has not been total — on several occasions, the Senate has sent a bill back to the House twice — even if the outright defeat of legislation by the Senate is rare: the last instance of a government House bill being rejected in the Senate occurred in 1996.

In response to Pratte's question, Liberal Senator Serge Joyal seemed resolute. "The question is a very important one," Joyal said, "but my answer would be, not at the expense of the rights of citizens who have recently been granted that right and are in a condition of intolerable suffering. It would be cruel to leave them in that condition."

Of course, whenever the Senate attempts to impose itself, it risks being condemned for thwarting democracy by those who oppose the particular changes it seeks. And so the degree to which it is able to get away with standing in the way might depend on how well it is able to stay on the right side of public opinion.

Senators might not directly answer to the public, but for the sake of the institution's continued existence, senators might aim to keep the upper chamber from seeming to be an overly entitled impediment to democratic governance.

Every assertive act of the Senate is a potential test of the chamber's legitimacy.

Ambrose says unelected Senate should not be changing laws1:44