There's so much teaching about legal grounds, but the word of God says, that Jesus has defeated the devil, took away his authority, but the devil does have 'power' but that power is given him through agreements.
The adversary walks around like a roaring lion seeking those whom he may devour. Who is he devouring? Those who accept his thoughts, his lies, his deceptions and speak like him. Can two walk together except they be agreed? Amos 3:3
For example, you said
please pray to reveal the legal grounds the demons have to remain in my life.
As a Christian, if you believe that demons have legal ground to remain in your life, then, sadly, that is where your faith is.
Jas_4:7 Submit yourselves therefore to God. Resist the devil, and he will flee from you.
Rom_8:2 For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.
Psa 103:2 Bless the LORD, O my soul, and forget not all his benefits:
3 Who forgiveth all thine iniquities; who healeth all thy diseases;
4 Who redeemeth thy life from destruction; who crowneth thee with lovingkindness and tender mercies;
5 Who satisfieth thy mouth with good things; so that thy youth is renewed like the eagle's.
Father, thank you for your mercy and grace. Thank you for your word that is Spirit and is life I pray for the spirit of wisdom and revelation be give this person, that their eyes be flooded with the light of your glorious gospel, that they would make a decision and walk in the freedom that you died to give them. They would jump into your word and meditate on it day and night, talk about your word, for it is life to those who find it and health to all their flesh. I bless this person with the truth in your word that sets them free to walk in the full stature of Christ in them, the hope of glory. In Jesus name. Amen.