Most sites will let you use a tournament marker
"BUT"
1=you won't be allowed to use ramping
2=sites make money by punters wasting paint by shooting and missing people with crap guns, if you turn up and shoot everyone out instantly then the site owner won't make any money and you'll never play there again
3=they will probably only have CO2
4=You'll need to provide air
5=flash guns upset the punters as they feel you have an unfair advantage, if you do the day in good spirits and maybe provide suppression fire for other players to make a move, then you won't get treated like an outsider.
6=we used to use tourney guns at our local recball site but then there was a group of us who always tried to take each other out first before we started on the punters.