Basel III defines capital, leverage, liquidity and net stable funding ratios
they're in the form of formulas, and regulations require minimum thresholds to be met
I previously wrote about Basel III and its importance in financial markets here โฌ๏ธ
https://illya.sh/threads/@1753631798-1.html
banks are also subject to regulations when issuing loans
and no - it's not the fractional reserve system
in many sovereigns, like the USA the reserve requirements sit at 0%
there are other regulatory requirements limiting loan issuance