Luftstalag14
Culé de Celestial Empire
Before every season in the DFL system (1st and 2nd division) clubs require a license, otherwise they can't start the season and enter forced relegation. There is handful of requirements to get the license, like stadium size, liquidity etc. Part of it is also debt. The German league is very strict in the amount of debt clubs can have, although they lifted the restrictions temporarily the past 2 seasons cause of Covid (still sanctioned indebted clubs though).
Short story: Should Barca for whatever super weird reason ever enter the German league, they'd absolutely not get a DFL license, and would have to go down to the 3rd league and can't ever promote until their debt situation is solved. Last time this happened was in 2000 to TeBe Berlin.
Good to know, but Schalke wasn't relegated simply because of its debt, was it?
Each country has its own rules, naturally. Spain has its salary caps and Germany has these requirements and I am sure other countries have theirs too. Still a silly remark from Hoeness to always talk down on others and that "here in Germany.." stupid stuff.