Gatekeeping

When someone takes it upon themselves to decide who does or does not have access or rights to a community or identity.

Gatekeeping is to make your interests exclusive in order to protect them from becoming “mainstream”

A word used to describe when someone sets a standard/limit on what someone must do to call themselves a 'true fan' of something/someone.

When someone uses a hobby or interest as a means of elevating themselves above others to give oneself a sense of being superior transforming their passion or knowledge about a particular subject into an ugly tool of self-inflation.
-GoodGuyFitz 2019

When someone takes it upon themselves to decide who has access to something

When someone limits people from certain hobbies/memories/activities over something as small as the year that they were born in.

Gatekeeping is frowned upon, so I don't recommend doing it. It's also a really stupid thing to do.

n. The practice of preventing the entry of bad actors into a fandom. The bad actors’ intent is to damage intellectual properties by forcing the IP owner to change the lore, alter the gameplay, or otherwise decrease the enjoyment of the IP by long-time, heavily invested fans. These bad actors typically have no interest in the intellectual property and are not willing to spend time or money to support the IP, but have a loud voice on Twitter or other social media, fooling IP owner into thinking they have more clout than they do. They usually join the fandom for political reasons or to damage the public image of the fandom.