Sweeney voiced his concern to the Prime Minister, Theresa May about British participation in the April 2018 missile strikes against Syria, calling for an “internationally policed no-fly zone" over Syria to stop the regime bombing its own population. In the wake of a series of veteran suicides in the summer of 2018, including from his former regiment, Sweeney criticised the British Army and Ministry of Defence for inadequate mental health support for former soldiers, and a lack of sufficient records to establish the scale of the problem, accusing them of ‘passing the buck’ to overstretched military charities like Combat Stress. In 2019, he began a campaign with the Royal British Legion and Earl Haig Fund Scotland, backed by the "Daily Record", calling on the UK Government to abolish immigration fees in the Immigration Act 2014 and Armed Forces immigration requirements as set out in the Immigration Act 1971, in order to allow over 6,000 personnel currently serving in the British Armed Forces from foreign and Commonwealth countries the free right to British citizenship, including the Brigade of Gurkhas. He served on the public bill committee that successfully oversaw the passage of the Armed Forces (Flexible Working) Act 2018 into legislation. Sweeney also successfully campaigned to restore the Highland Light Infantry memorial in Kelvingrove Park after it was vandalised in February 2019.