Conrad Black has reflected publicly on the 28 months he spent in a federal prison in Florida. (Charles Rex Arbogast/Associated Press)

Conrad Black has slammed the U.S. justice system as he reflected publicly on the 28 months he spent in a federal prison.

"Of course, I was glad, jubilant, to leave … but also grateful for many of the relationships I had formed; enlightened by my observation of American justice on the other side of the wall; and happy to have got on well in an environment very foreign to any I had known before," Black wrote in a column for the National Post.

During his time at the federal prison in Coleman, Fla., Black, 65, said he developed a greater practical knowledge of the realities of race relations, of those "who had drawn a short straw" from the justice system and of the "wasted opportunities" to reintegrate many of those prisoners into society.

The former media mogul said he saw the "courage of self-help, the pathos of broken men, the drawn faces of the hopeless, the glazed expression of the heavily medicated." He described America's inmates as an "ostracized, voiceless legion of the walking dead."

He lashed out at the U.S. war on drugs, saying it's a failure and that the long sentences are absurd and unjust.

Last week, Black was released on a $2-million bond from the prison where he was incarcerated on fraud and obstruction charges.

He said the day he left prison, inmates who streamed in to say goodbye included drug dealers, Mafiosi, pornographers, credit card fraudsters, bank robbers "and in almost all cases the grossly over-sentenced."

"Most goodbyes were brief and jovial, some were emotional, and a few were quite heart-rending," he said.

Black said he was "delighted" to be back home at the Palm Beach mansion he rents, saying the first night he "enjoyed pristine quiet, free of loudspeakers, screamed argument, and the snoring of a hundred men. I had a glass of wine, and waited for Barbara, to celebrate the happiest of all wedding anniversaries."

Black is seeking to return to Canada, but the judge overseeing his bail hearing in Chicago has said she needs more detailed information on his finances. He returns to court Aug. 16.