It always annoys me when news articles about laws neglect to mention the number of the law (which would allow us to look it up and read it directly). So I went looking, and found it: it's complementary municipal law 993/2023 (
https://legislacao.portoalegre.rs.gov.br/norma/47673), which adds a single article to complementary municipal law 170/1987 (
https://legislacao.portoalegre.rs.gov.br/norma/24099). As you can see if you download the docx in the first link, it's a single page, which contains a pair of articles written in a very boilerplate way (the first article inserts a new article, with three paragraphs, into the other law, and the second article says that the law takes effect immediately once published).