I already asked an admin about this, it is allowed. But, with all the seriousness, putting claymores near the flag gives you easy kills.
Imagine someone running two minutes to get to the desired flag and he steps on a hidden claymore. This is so frustrating.
The key role of the claymores is to defend your position if you find a good sniping spot.
I hope this will change one day, it is so pissening. I have seen few guys making half of their score out of flag claymores, you can easily put an entire squad down if they are near each other.