Nope, INVALID !

The ONLY way to slow down the levelling process is NOT TO PLAY.

I've levelled a federation admiral in 6 weeks from Captain and ONLY did the lore and daily foundry missions, and NEVER once left SOL system.

I levelled an entire new KDF toon in a week without even trying.

There is NO way to stop the levelling, but if you dont upgrade your ship/weapons you'll quickly be outclassed by the A.I. that matches your toon level.