Put up a page saying you support "Palestine Action". Given that group is (currently) a proscribed "terrorist organisation" (and therefore illegal to support, obvs.), your page would definitely be illegal in the UK.
(Although I suppose there's the light risk that MI6 might decided to rendition you with $LOCALCOUNTRY's assistance if they're feeling exuberant.)
Vandalism, property damage and trespassing. Illegal, sure, but terrorism? Really now...
I'd put that up on a page.