Why wouldn't the others be ok ? You do not need "express allowances" to do this. Any-more-so than you need express allowances to fly frisbees. If it's silent on the subject (no prohibitions) and no mention of permits for it, then ..... presto, it's allowed. You are not going to see signs at the park or beach saying "md'ing allowed here".
Oh, but if you're
REALLY REALLY uncomfortable going unless you see a rule, then ... ok then: Here's a rule you need to know: You must send me 30% of all your finds (I accept paypal). Ok, now go find some good stuff