I swear by my…
Eleven year old Hermione Granger was fascinated by the book she was currently reading. She had recently been visited by a woman called Professor McGonagall who had explained to her and her parents that she was a witch and could do magic, naturally this had been a great shock to her family and quickly denied, but a quick demonstration of magic had destroyed those doubts.
Her visit to Diagon Alley was incredibly exciting, visiting the goblins, which weren't at all like she imagined them to be, buying potions ingredients, getting fitted for robes, her mum had marvelled at the other options and had bought something called a Flash Dress guaranteed to tease to your partner when you thought of it and a bunch of outfits that apparently were self-cleaning and repairing, she didn't know why her mother needed a maid outfit or a nurses uniform but she was sure her dad would tell her.
Getting her wand had been a nerve racking affair this was the moment when she would prove herself a witch, eight and three quarter inches vinewood with dragon heartstring was what she achieved after three unsuccessful wands.
Finally came Flourish and Blotts, the sheer number of books available was breathtaking, after buying all her school books and a small guide book on suggestion from Professor McGonagall, she had bought another half-dozen books on thing that had seemed interesting. McGonagalls mention of a war that had ended a decade ago had her buying a book on it.
*BIG*
This was the book she was currently reading; she had gotten to a section on security measures taken by the Ministry of Magic to combat the Death Eater threat, specifically the section on magical oaths. Apparently the Ministry had set up a system where every witch and wizard in the country had to come into the Ministry when requested and swear a magical oath that they weren't part of the group known as the Death Eaters, aiding the terrorist group known as the Death Eaters knowingly or a follower of the man known as he-who-must-not-be-named, you-know-who or Lord Voldemort, failure to comply with this law resulted in an immediate warrant for arrest, a fine and a bounty been placed on your head.
Hermione nodded her head at the sensibility of the magical government at least they knew how to take combat a terrorist threat living amongst the population.
Authors note: This is how I would see the usage of Magical Oaths been used in HP canon if they were actually a thing that existed in HP canon.
No denying it and a quick trial if you refuse to make the oath, you can have a small group of authorised Aurors and Obliviators go through your head if you suspect you have been memory wiped or had a compulsion placed on you and then will receive a more specialised oath to swear if foul play is found.