At one time in common law history, the rule of interspousal immunity ruled the day. That doctrine held that husband and wife could not sue each other in civil litigation and all litigation from a third-party against the one was liable against the other. Blackstone explained it this way:

By marriage, the husband and wife are one person in law that is, the very being or legal existence of the woman is suspended during the marriage, or at least is incorporated and consolidated into that of the husband: under whose wing, protection, and cover, she performs everything; and is therefore called in our law-french a feme-covert [married woman]; is said to be covert-baron, or under the protection and influence of her husband, her baron, or lord; and her condition during her marriage is called her coverture. Upon this principle, of an union of person in husband and wife, depend almost all the legal rights, duties, and disabilities, that either of them acquire by the marriage.

Upon entering into the marriage covenant, the husband, under this doctrine “became liable for the torts of his wife, committed either before or during the marriage,” and — strikingly enough — he became “liable to himself for his wife’s torts against him.” (W.L. Prosser, Torts ch. 23, § 122 (4th ed. 1971) at 860, Prosser, Torts ch. 12 (12 ed.) at 648).

Modern courts have since moved away from this legal protection of the marriage unit, either abrogating it in toto or partially through various circumstantial limitations (such as intentional torts or automobile accidents). However, the theological truths relating to such spousal immunity is nothing less than transcendent.

The reason this is true is the reality that the redeemed people of God are revealed in Scripture as the bride of Christ. In Ephesians 5, the Apostle Paul writes:

Wives, submit to your own husbands, as to the Lord. For the husband is the head of the wife even as Christ is the head of the church, his body, and is himself its Savior. Now as the church submits to Christ, so also wives should submit in everything to their husbands.
Husbands, love your wives, as Christ loved the church and gave himself up for her, that he might sanctify her, having cleansed her by the washing of water with the word, so that he might present the church to himself in splendor, without spot or wrinkle or any such thing, that she might be holy and without blemish. In the same way husbands should love their wives as their own bodies. He who loves his wife loves himself. For no one ever hated his own flesh, but nourishes and cherishes it, just as Christ does the church, because we are members of his body. “Therefore a man shall leave his father and mother and hold fast to his wife, and the two shall become one flesh.” This mystery is profound, and I am saying that it refers to Christ and the church. – Ephesians 5:22-32

Marriage, in Scripture, is a picture of the relationship of Christ and his Church. This becomes of infinite importance when we consider the kind of spiritual immunity that Christians receive once we are united to Christ in faith, and become members of his Church. In the same way that a husband under common law was “liable for the torts of his wife, committed either before or during the marriage,” when Christ redeemed us to be his Beloved people, every sin that we committed (or will commit) against Him and others was accounted to Him. As the Apostle Paul explains it in 2 Corinthians 5:21, “For our sake [the Father] made Him to be sin who knew no sin, so that in Him we might become the righteousness of God.” Although modern courts have subsequently let go of interspousal immunity in civil law, the court of Heaven has declared the blood-bought immunity we have in Christ still “good law” (and always will be). And this is an encouragement that every Christian would do well to remember…

“…for all have sinned and fall short of the glory of God, and are justified by his grace as a gift, through the redemption that is in Christ Jesus, whom God put forward as a propitiation by his blood, to be received by faith. This was to show God’s righteousness, because in his divine forbearance he had passed over former sins. It was to show his righteousness at the present time, so that he might be just and the justifier of the one who has faith in Jesus.” - Romans 3:23-26