Before signing in the anti-gay laws, Ugandan President Yoweri Museveni said that he was privy to scientific "facts" saying: "No study has shown you can be homosexual by nature."
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The talks descended into crisis on Friday when Canada's trade minister Chrystia Freeland walked out of meetings.
Police in New York are still investigating what the substance is and whether it could be harmful.
The Sherlock actor made the comment while he received an award for his humanitarian work.