It depends on what picnic items you're talking about. With current world issues the way they are, they check bags for certain items very well.
They discourage any outside carry-ins. If they see it.. they will take it!
No cans or bottles
They did look throw some bags checking but not all people got checked I did not
They didn't look through our backpack when we went a couple weeks ago, but I'm not sure if you could bring a cooler in or not.
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