EF6 and NPGSQL: Foreign key violation error

Good afternoon! I'm new to ASP.NET and EF6. Developed earlier in PHP.

I created a project (ASP.NET MVC) using EF6 and NPGSQL. I picked up a little while creating the relationships between two tables but it worked. The persona table will have several countries (1: n). It follows SQL, Model and context.

SQL:

 CREATE TABLE pais(
  idpais character(3) NOT NULL,
  nomepais character varying(100) NOT NULL,
  CONSTRAINT pk_pais PRIMARY KEY (idpais),
  CONSTRAINT ix_nomepais UNIQUE (nomepais)
)

CREATE TABLE persona
(
  idpersona serial NOT NULL,
  nomepers character varying(100) NOT NULL,
  idpaispers character(3),
  CONSTRAINT pk_persona PRIMARY KEY (idpersona),
  CONSTRAINT fk_perspais FOREIGN KEY (idpaispers)
      REFERENCES pais (idpais) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION,
  CONSTRAINT ix_nomepers UNIQUE (nomepers)
)

Model Parents

[Table("pais",Schema="public")]
public class Pais
{
    public Pais()
    {
        this.Persona = new HashSet<Persona>();
    }
    [Key]
    [Column("idpais")]
    [Display(Name = "Sigla")]
    [DataType(DataType.Text)]
    [StringLength(3)]
    [Required]
    public string IDPais { get; set; }

    [Column("nomepais")]
    [Display(Name = "Nome")]
    [DataType(DataType.Text)]
    [StringLength(100)]
    [Index("ix_nomepais",IsUnique=true)]
    [Required]
    public string nomePais { get; set; }

    public virtual ICollection<Persona> Persona { get; set; }
}

Model Person:

    [Table("persona", Schema="public")]
public class Persona
{
    [Key]
    [Column("idpersona")]
    public int IDPersona { get; set; }

    [Column("nomepers")]
    [Display(Name = "Nome")]
    [DataType(DataType.Text)]
    [StringLength(100)]
    [Index("ix_nomepers", IsUnique = true)]
    [Required]
    public string nomePers { get; set; }

    [Column("idpaispers")]
    [Display(Name = "País")]
    [DataType(DataType.Text)]
    [StringLength(3)]
    public string idpaisPers { get; set; }
    public virtual Pais Pais { get; set; }

}

Context:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<Persona>()
                .HasRequired<Pais>(p => p.Pais)
                .WithMany(e => e.Persona)
                .HasForeignKey(e => e.idpaisPers);
}

When it comes to including a "persona", I purposely specify a country that is not registered, generating a Postgres foreign key violation error. But should the EF not validate before? Did I miss something or should I include a validation so that this error does not occur? Thanks in advance for anyone who can help.