Legal and licensed, province by province
Argentina regulates online gambling at provincial level rather than federally. The City of Buenos Aires licenses through LOTBA, Provincia de Buenos Aires through IPLyC, and other provinces run their own registers.
What that means in practice: an operator can be fully licensed for CABA and not licensed where you actually live. The licence that protects you is the one covering your province, and it is checkable on the regulator's public register.
Operators without any provincial licence are reachable but sit outside that protection, which is the difference that matters if a withdrawal is ever refused.
What follows in practice
The licence is checkable. LOTBA (CABA) and provincial regulators publishes a register, so "licensed" is a claim you can confirm in about a minute rather than take on trust.
Unlicensed sites are still reachable. They sit outside the framework, and the difference shows up at withdrawal rather than at deposit.
Tax and reporting are your responsibility. This site does not advise on either.
How to check an operator yourself
Whatever the position above, the check is the same and takes about a minute.
Find the licence number on the operator’s site — usually in the footer, often as small text next to a badge. Then look that number up on the regulator’s own register rather than trusting the badge, which is only an image and can say anything. If the number is absent, or present but does not resolve, treat the claim as unmade.
The second check costs a little money and is worth more than the first: deposit a small amount, play briefly, and request a withdrawal. What you learn is not the speed but whether the process works at all, what verification gets demanded and how support behaves when money is leaving rather than arriving.