Could the accused use the fact that the US has ratified the 1967
protocol in defense, despite the fact that the protocol's protection
against penalties for illegal entry is not explicit in US law?
Is The Protocol Self-Executing?
There is one main potential difficulties with this particular defensive theory.
Many international agreements are interpreted by the courts to be not "self-executing" which is to say that they are agreements to pass compliant domestic laws and policies, rather than directly creating rights for individuals. In contrast, if it is self-executing then it can be used as a defense.
The legal effect of the 1967 Refugee Protocol, "Protocol relating to the Status of Refugees", 19 U.S.T. 6223, 606 U.N.T.S. 267 (January 31, 1967), and in particular the question of whether it is self-executing is disputed, at least, academically.
But, a State Department legal opinion which has not clearly and explicitly been overruled by the courts, states that it is not self-executing, despite the fact that a lower Article I court in In re Dunbar, 141. & N. Dec. 310 (Board of Immigration Appeals 1973), had previously held that the Protocol was self-executing (despite ruling against the immigrant on the merits in interpreting the obligations created under the Protocol).
The issue was raised and not resolved in a case related to mass migration from Haiti during the George H.W. Bush administration, but that issue was not reached in the judgment in that case. This position was supported by a 1991 State Department legal memorandum, which claimed that the 1967 protocol was not self-executing. A law review article from 1993 examined this issue rather comprehensively, questioning the conclusion of the State Department Memo. A 1997 law review article argues that it does have binding effect but that the U.S. has erroneously failed to treat it that way in either the courts or in some of its administrative policies.
The thrust of the executive branch legal opinions and case law regarding the Protocol appears to be that it is not self-executing.
The Protocol As A Guide To Statutory Interpretation
On the other hand, even though there is not an explicit U.S. law statute providing a defense to illegal entry, one could argue that since refugee status is recognized in the U.S. that the entry is not illegal. And, the Refugee Convention could definitely be used as evidence of legislative intent in interpreting the law to determine if U.S. law implicitly prohibits such a prosecution, in the face of the question of whether or not other legal authorization to give someone refugee status makes the entry not illegal.
In particular, "it is absolutely clear that the passage of the Refugee Act of 1980 [Pub. L. No. 96-212, 94 Stat. 102] was intended to implement American obligations under the Protocol." (from a 2000 law review article). For example, three of the leading cases interpreting the 1967 Protocol and the Refugee Act of 1980 (with a largely anti-immigrant outcome on the merits) are INS v.Aguirre-Aguirre, 119 S. Ct. 1439 (1999) and INS v. Cardoza-Fonseca, 480 U. S. 421 (1987), and INS v. Stevic, 467 U.S. 407 (1984) (limiting refugee litigation rights), still purported to interpret the Refugee Act of 1980 in light of the fact that it was intended to implement the Protocol.
In addition to the Refugee Convention, the long standing practice (until the current administration) of neither immediately deporting nor prosecuting people who claim refugee status for illegal entry would also argue in favor of this interpretation.
An agency's historical and traditional custom and practice in applying a law is an important part of interpreting laws in which the agency, at the outset, has considerable discretion to resolve ambiguities regarding its meaning, although existing policies and positions of the agency are also entitled to deference.
Furthermore, when Congress amends a law, it is presumed to know the way that the law is currently being interpreted by the Executive Branch and the Courts, and to ratify those positions if they are not changed.
Any argument referencing the Refugee Protocol would also have to establish under the currently applied precedents that the purported refugee has, or at least is likely to have, a well founded fear of persecution in the country from which they are fleeing. Likewise, the refugee would have to prove that exceptions to the general rule (e.g. national defense and prohibitions on alien non-political criminals) do not apply.