Robert Kyagulanyi hires US law firm Robert Amsterdam.
Ugandan independent MP and musician Robert Kyagulanyi has hired a US law firm, lawyer Robert Amsterdam has said in a statement.
Mr Amsterdam described his client's arrest as a "politically motivated act of repression" and alleges that he has been tortured in custody.
The army, which is holding Mr Kyagulanyi, denies that he has been tortured and President Yoweri Museveni has dismissed the claims as "fake news".
Mr Kyagulanyi, also known as Bobi Wine, won a by-election last year.
He has been held since last week, along with four fellow MPs and dozens of others.
They were campaigning in a bitterly contested by-election in Arua in the north of the country.
Mr Amsterdam is recommending that the US should "hit [government] officials in their wallets with a Magnitsky-style sanctions schedule as they need to understand the consequences of this attack on human rights”.
The US Magnitsky Act allows Congress to impose sanctions on human rights abusers anywhere in the world.
Earlier on Wednesday, Deputy Speaker of Parliament Jacob Oulanya visited Mr Kyagulanyi at the Makindye Military Barracks.
Mr Oulanyah confirmed the MP's poor state of health.
“I talked with Hon Kyagulanyi but he is in a lot of pain. He is however in a uniquely humorous mood and we were laughing with him,” Oulanyah is quoted as saying.
In a 8-second clip circulated widely on social media, Kyagulanyi is seen in a red shirt and pair of shorts with slippers siting around a plastic table laughing but with apparent difficulty.
Mr Kyagulanyi is due to appear in court on Thursday on charges of illegal possession of firearm and ammunition.
— Additional reporting by Charles Mpagi.