The pins can certainly be jammed in the lock due to exposure. Especially if it has been on the ground very long. Flush the lock out with a few sprays WD40 until they free up. After the WD40's temporary status as a lubricant wears off, then you will need a replacement lube. A tiny puff of graphite for locks that you intend to put back into use is recommended. Graphite powder is dry, so in theory it doesn't collect foriegn debris in the lock. It just becomes debris when you use to much, or expose it to airbourne moisture.
Locks I keep for picking always get a tiny amount of silicone or oil based lubricant if they are stiff due to friction because it feels so smooth, and it's easier to measure the amount you apply without getting graphite fingerprints all over the place.
-Tooly
