Is "latest rules" truly what happens? Or if the law explicitly allows X and also explicitly disallows X, then a person would not be convicted, rendering in this case the latest safeguards in effective?
To say it's complicated is an understatement, there are literally entire books written about it [1]. It's rarely that simple but if one act states X is allowed and another act of the same jurisdiction states the exact opposite (assuming both laws are legally valid), then the most recent law prevails. The principle behind it is that the current parliament/legislature shouldn't be able restrict what future parliaments make laws on (the exception being the Constitution). Otherwise the government of today could make a law thats says 'X is illegal and no law can ever change this'.
[1] https://www.federationpress.com.au/bookstore/book.asp?isbn=9...
[edit: typos]