It is obvious that the president cannot through executive orders change the operations of the Immigration and Nationality Act by fiat. But what he can do under the separation of powers is to determine how the Act is to be implemented. Thus President Obama was constitutionally able to determine that he would no longer accept Cubans applying for asylum at the border by simply paroling them into the United States. If paroled Cuban applicants could for residence under the Cuban Adjustment Act of 1966. Now Cubans applying for admission must undergo the same procedure as other asylees which includes detention and a hearing while detained to determine if they fit the statutory definition of asylees. This procedure may result in immediate removal after the hearing since few Cubans now have legitimate asylum claims.

However the executive orders must still pass constitutional muster. Thus executive orders banning persons from several countries that are primarily Muslim runs afoul of the First Amendment. Therefore executive orders must still fit within the separation of powers without which there can be no democracy.

​So the bottom line is that executive orders are really nothing more than administrative or prosecutorial decision as to how to apply the Immigration and Nationality Act. decisions by the 

Matter of Gonzalez Romo, 26 I&N Dec.  743 (BIA 2016)

Within the jurisdiction of the United States Court of Appeals for the Ninth Circuit, a
returning lawful permanent resident who has a felony conviction for solicitation to
possess marijuana for sale is inadmissible under section 212(a)(2)(A)(i)(I) of the
Immigration and Nationality Act, 8 U.S.C. § 1182(a)(2)(A)(i)(I) (2012), even though that
section refers only to attempt and conspiracy to commit a crime involving moral
turpitude, and is therefore properly considered to be an arriving alien under section
101(a)(13)(C)(v) of the Act, 8 U.S.C. § 1101(a)(13)(C)(v) (2012). Matter of Vo, 25 I&N
Dec. 426 (BIA 2011), clarified.

Matter of Garza-Olivares , 26 I&N Dec. 736 (BIA 2016)

In assessing whether an offense qualifies as an aggravated felony under section
101(a)(43)(T) of the Immigration and Nationality Act, 8 U.S.C. § 1101(a)(43)(T) (2012),
the categorical approach applies to decide if the offense relates to an alien’s failure to
appear before a court, but the circumstance-specific approach applies to determine if the
failure to appear was (1) pursuant to a court order (2) to answer to or dispose of a charge
of a felony (3) for which a sentence of 2 years’ imprisonment or more may be imposed.

Matter of Villalobos, 26 I&N Dec. 719 (BIA 2016)

The BIA has jurisdiction to decide whether a respondent is removable under section 237(a)(1)(A) of the Act as an alien who was inadmissible at the time he adjusted status under section 245A(b)(1) of the Act. The provisions of 245A make clear that an applicant must establish admissibility, not only to initially become a temporary resident, but also to adjust status to that of a permanent resident. An alien who was inadmissible at the time he was granted adjustment of status under section 245(A)(b)(1) is ineligible for 212(c) relief because he or she has not been lawfully admitted for permanent residence.

Matter of Guzman-Polanco, 26 I&N Dec. 713 (BIA 2016)

The Board held that regardless of the name of  the statute it is not a crime of violence unless an element of the crime is the use, attempted use or threatened use of violent physical force. The Board withdrew Matter of Martin, 23 I&N Dec. 491 (BIA 2002).

Thus a conviction for the crime of aggravated battery under the Puerto Rico Penal Code is not a crime of violence because it does not require the use of physical force.

Matter of Mendoza Osorio, 26 I&N Dec. 703 (BIA 2016)

The BIA found that because the offense of endangering the welfare of a child in violation of section 260.101(1) of the New York Penal Code requires knowingly acting in a manner likely to be injurious to the physical, mental or moral welfare of a child is categorically a crime of of child abuse, child neglect or child abandonment pursuant to section 237(a)(2)(E)(i) of the Immigration and Nationality Act.

Any state statute which defines child abuse as requiring actual knowledge and the likelihood of harm rather than the possibility of harm will following this case constitute a categorical crime of child abuse. To fall outside the categorical definition Respondent must prove that there are convictions under the pertinent statute that do not constitute child abuse under the Act.