well they are now specifically banned due to the bill passed last year, but this is from motherwells website fir park rules
11. The use threatening behavior, foul or abusive language is strictly forbidden. Racist, homophobic, discriminatory or sectarian remarks, songs or chants; and the promotion or endorsement of any political or proscribed terrorist organisations is not permitted within the stadium and may result in arrest and a lifetime ban from regulated football matches.
thats always the case at every ground, uefa hand down dictats which they expect national associations to adhere to, one of them and its not a new one is no poitical protests of any form within any ground ever, thats a big no-no, this would naturally include political songs, or any song pledging alleigance to any political organisation.