JR said:
So last night I was all excited because I add ring seat to an NHL game in Montreal so I thought lets bring the 5D mkII with my 135mm and take some cool shots right! I see so many sports pictures being posted here that I thought this would be fun!
Well when I got to the door the security denied me access to the sport center because my camera has detachable lens (the G1X would have been handy!)! The guy was fairly rude so I could not figure out why except that I was not a certified journalist. So I had to bring back the camera to the car and come back empty handed to get in :-[ !
Is it like this for all professional sports? What is your experience shooting pro sports? Do we need some kind of accreditation or did I just stumble onto a bad security person?
...by the way two rows down from me was a professional photographer using his Nikon D3s though ... 
It really depends upon the sport and the stadium.
Red Bulls soccer bans everything and anything. Philadelphia Union allows in DSLR with lenses as large as 70-300L.
NCAA D1 Women's College Cup and NCAA ACC Women's Tournament Soccer banned even rebels with pancake lenses these days, even friends and family and fellow students, no go, pretty ridiculous I mean it's college sports let the people have their fun, isn't that what college is supposed to be about? and it's not even like they are the big revenue sports basketball and football are. While OTOH at Yankee Stadium they allow in DSLR without issue and you see 70-200,70-300,300 f/4, 400 f/5.6, etc. all the time all over the place.
(regular season NCAA soccer games though tend to very lax though, i've seen people with super-tele in the stands, but again it depends upon the place and the setup)
D3 colleges are often more lax about things, but it depends. Sometimes you can use super-tele, at the schools where sports aren't much of a big deal and attendance, even for football, is almost non-existent, it depends, not that it's a total free for all even there since they don't want people doing silly things and causing havoc or injury, but at some you can all but shoot from field in more or less pro positions, although at most you'd absolutely need a press pass for anything close to that.
In some cases bans are because everyone is so lawsuit happy these days, so no monopods even for field seating at soccer, in case you trip someone and then the stadium would get sued.
The places that ban lenses over 8" sometimes do it because they don't want people swinging long lenses and blocking other fan's views and not necessarily for other reasons.
NBA tends to be super restrictive (even with a press pass, for pre-season game, it's so restrictive that you often are not even allowed to so much as share shots on the web or even share them with other news agencies, some passes say the images can on;y be presented by the designated media outlet on the pass alone). NFL is often pretty restrictive. WPS is a mixed bag ranging over the entire gamut, from relatively lax to 100% restricted. MLS is mixed too although a bit more restrictive on average. MLB tends to be relatively lax about it, on average, they are much less strict than the NBA/NFL/NHL, much less so, but I have heard that in some MLB parks they are somewhat strict.
MLB is your best bet above the high school level (but do check since it does vary stadium to stadium).
or a sport that isn't getting love. Even at a D1 school, some sports, for some reason get little attention paid to them. I know one school where tennis was desperate to get a look, if you can show that you are capable of getting some decent shots they might let you in with whatever you want. Look at the local papers and the school's paper, if some sports rarely gets photos in the paper, they may be open to things.
