I don't have a dog, but I'm a 1L with cats, so I'm going to weigh in here. I haven't read all 3 previous pages, so my apologies if I'm repeating stuff people already said.
Not having my cats was never an option for me. I'm sickly attached to them, and even brought one with me when I moved to Europe last year. They also help to de-stress me and make me incredibly happy, and I am so thankful that I have them.
That said, there are definitely sacrifices you have to make, even with cats. During finals I was basically only coming home to sleep, and a lot of times I would have to adjust my study schedule/when I was going to come home based on when I needed to feed them. I also totally neglected them attention-wise during exams. When finals were finally over, I woke up every morning to both of my cats laying on top of me because they were so happy I was home.
Another consideration is, if you're not from near where you're going to law school, you will need to figure out what to do with the pets when you go home for breaks.
And finally, money. Pets are expensive, and loans don't really give you a ton of money to life on.
That said, if you have really thought over everything and know you can do it, go for it. My cats definitely help with my mental health.