I know there have been meetups in Oceanside before and I believe this ordinance has been vetted before however, I don't remember the outcome.
The city of Oceanside municipal code chapter 20 section 10 states:
No person shall be or appear in any street, alley, sidewalk, parkway or any public place or place open to public view while carrying upon his person, or having in his immediate possession, any dangerous or deadly weapon. This section shall not be construed to duplicate prohibitions of California state statute, or to prohibit the possession of weapons expressly authorized by California state statute.
So is this enforcable or somehow preempted by State law?
A citizen may not be required to offer a ―good and substantial reason-- why he should be permitted to exercise his rights. The right‘s existence is all the reason he needs.